This invention relates to a camshaft and a method of manufacturing the same, and more particularly, to a camshaft capable of being used for a high pressure engine and a method of manufacturing such camshaft effectively with low cost.
In general, as a camshaft for an engine, there is a widely known so-called cast iron chilled camshaft in which a chilled carbide is formed on a sliding surface of a cam portion by rapidly quenching the cam portion by means of a chill.
Recently, in accordance with an improvement of an engine with high performance, there has been required to provide a camshaft for a high pressure engine having high abrasion resistant property and high scuffing resisting property.
However, these properties are not sufficiently attained by the above-mentioned cast iron chilled camshaft. For example, there has been used a remelting chilled camshaft which is formed by irradiating a laser beam onto a once chilled cam portion and then again performing a chilling operation, or a camshaft which is formed of a cast steel or sintered material.
However, in a conventional so-called cast iron chilled camshaft, there exist limitations in refining of the chilled carbide, carbide area rate and hardness of the carbide, so that it is extremely difficult to further improve the abrasion resistant property and the scuffing resisting property more than those in the present technical level.
Furthermore, in the above-described remelting chilled camshaft, an equipment, for example, for performing an irradiation of laser is additionally required, involving a manufacturing cost increasing.
Still furthermore, the above-described camshaft formed of the cast steel or sintered material has a material cost higher than that of the cast iron chilled camshaft, thus also providing a problem.